Drug Induced Sleep Endoscopy in Obstructive Sleep Apnea

Background: One of the main challenges of surgical treatment in Obstructive Sleep Apnea (OSA) is identifying the correct site of upper airway obstruction in an individual patient. Drug-Induced Sleep Endoscopy (DISE) in sedated patients with obstructive sleep apnea is the technique of choice for revealing anatomic and dynamic collapsible areas. Materials and Methods: In a prospective cross-sectional study adult patients with OSA documented by polysomnography were evaluated by sleep endoscopy. DISE had been done by an otolaryngologist in the setting of operating room during infusion of propofol and after the start of snoring. Endoscopic findings were recorded and evaluated from the aspect of obstruction level, severity, and multiplicity. Results: Twenty OSA patients (60% men) with mean±SD age of 38.9±9.26 years and mean Body Mass Index (BMI) of 26.57 kg/m2 were included in the study. OSA was severe in 11(55%) and moderate in 5(25%) subjects. Unilevel airway collapse was observed as retropalatal in 4(20%) and retrolingual in 3(15%) subjects. Multilevel collapse had been observed in the other 13(65%) patients. Most patients (65%) had multilevel obstruction especially those with BMI>30 (p<0.05). With increasing BMI, obstruction changed from unilevel to multilevel. None of the subjects showed complications with propofol or endoscopy procedure. Conclusion: Our study showed DISE is safe, easy to perform, and informative in OSA patients. In particular, we observed a significant association between obesity and multilevel upper airway collapse.


INTRODUCTION
Drug-Induced Sleep Endoscopy (DISE) as a validated study is widely used in determining surgical approach in Obstructive Sleep Apnea (OSA) (1). Although endoscopy during physiologic sleep is the ideal procedure for evaluating the site of airway collapse, but it is unpleasant to patient and impractical for physician. Drug-induced sleep endoscopy has been introduced in 1991 in order to overcome these limitations (2).
Physiology of airway collapse in wake state has been shown to be different from induced sleep with only 25% coherence between results of wake and sleep endoscopy (1). Mapping of dynamic upper airway collapse during sleep is a key point in OSA patients who are candidate for TANAFFOS Sharifian MR,et al. 123 Tanaffos 2018; 17 (2): 122 -126 surgical treatment (3). Although induced sleep has its own drawbacks DISE has been validated as a useful tool in improving surgical success (4,5).
We planned this study to assess safety of DISE in our population and to compare the results of clinical and diagnostic evaluations with those of sleep endoscopy. We also evaluated the correlation between clinical parameters and levels and patterns of obstruction..

Study design and participants
This is a prospective cross-sectional study on patients

Baseline clinical assessments
After clarifying the aims and methods of the study and subscribing a written informed consent by the patients, they received a full otolaryngologic examination to evaluate wake status of upper airway and in particular size of uvula, soft palate and tonsils, tongue base, vallecula; size and shape of epiglottis, the degree of upper airway crowding (scored as Mallampati score) and state of mandibular occlusion (retrognathia, prognathia or normal occlusion). Although subjects were not necessarily candidates for surgical treatment of OSA, they were examined by an anesthesiologist before preparing for DISE. Patients were asked to sleep at least 6 hours the night before scheduled DISE day.

Demographic characteristics [including age, sex and
Body Mass Index (BMI)] along with data on the level of daytime sleepiness assessed by Epworth Sleepiness Scale (ESS) were gathered. Patients were categorized as sleepy and non-sleepy according to their ESS score (0-9 and 10-24, respectively). In the case of severe desaturation (O2 saturation<88%) mandibular advancement maneuver (jaw thrust) had been done by anesthesiologist to resolve the obstructive event temporarily.

Outcome measures
Our main outcome measure was the level of upper airway obstruction. Level of obstruction was defined as retropharyngeal, retrolingual, retropalatal and type of obstruction as circular, antero-posterior and latero-lateral.
We also classified the subjects according to the number of obstruction levels as unilevel and multilevel (more than

Demographic and anthropometric results:
Thirty-two subjects with OSA were included in the study. Twelve subjects (not subscribing written consent) were excluded. Of the remaining 20 patients with age range of 26 to 63 years (mean 38.9±9.26) and mean BMI 26.57kg/m2, 12 (60%) were male (Table 1).

Level and type of obstruction:
Multilevel collapse was observed in 13 subjects (65%).
The site of obstruction in those with unilevel collapse was retropalatal and retrolingual (20% and 15% of total subjects, respectively). The most common (50%) place of obstruction in cases with BMI<30 was retrolingual, while 100% of cases with BMI>30 showed multilevel obstruction

Sleepiness results
Seventy-two percent of subjects with severe OSA were placed in sleepy group (ESS≥10), but OSA severity was not different between sleepy and non-sleepy groups (p=0.45).
There was no significant correlation between the level of obstruction and ESS. We also found weak agreement between ESS and AHI (kappa=0.18; p=0.45).

DISCUSSION
To the best of our knowledge this is the first report of Other studies reported antero-posterior (9) and laterolateral (10) as the most common type.
In our study obesity was significantly associated with multilevel obstruction. Abdullah et al. also observed a trend of higher BMI with≥4 sites of obstruction compared to single-site obstruction (6). This study showed the appropriateness and reliability of the results obtained by DISE with their correlates obtained by polysomnography in an Iranian population.
Follow up study focusing on correlation of DISE results with surgical outcomes will determine its clinical importance more.

CONCLUSION
Our data suggest that DISE is safe and easy to perform, as previously reported. Furthermore, we found a good correlation between DISE findings and clinical characteristics such as BMI in agreement with literature data.

Financial Disclosure
No financial disclosures

Conflict of Interest
None

Patients' ethical consideration
All procedures performed in studies involving human